If the race for the 2016 GOP presidential nomination were all about headlines and buzz-worthy antics in 2013, Sen. Rob Portman certainly would be losing.

While some of the Ohio Republican’s colleagues with national ambitions have made news with 13-hour filibusters and by awkwardly reaching for water during nationally televised events, Portman has been relatively quiet. The former George W. Bush administration official and top Mitt Romney surrogate has been offering counsel to colleagues on budget issues and is giving personal assurances to big-ticket donors around the country that the National Republican Senatorial Committee won’t botch another chance to take back the majority.

Portman is also trying to figure out what’s next, a topic he’s loath to discuss publicly but mulls privately, according to those close to him.

In the first week of March alone, Portman took a phone call from President Barack Obama, then jetted to New York where he held five meetings with about 50 Republican donors, who he said all have serious concerns about the NRSC’s quality control of candidates. Meanwhile, Portman has been preparing to emerge as a prominent critic of the White House on fiscal matters, as well as of the Democratic budget, set to be rolled out this week.

“I’m constantly working with anybody who’s serious about [economic issues],” Portman told CQ Roll Call in a wide-ranging interview on March 6, the afternoon before 12 GOP senators dined with Obama.

That remark was aimed squarely at the president. Portman said he did not attend the Washington, D.C., dinner because he is not interested in a White House charm offensive.

“The president called me over the weekend, and I said I appreciated the call, but I want to know that it’s serious, and if it is, I’m all ears,” Portman said. “My interest is doing the hard work to get something done. ... The president’s job in my view is to provide political cover to Democrats to do what many of them know has to be done.”

Portman is most comfortable rattling off statistics about the deficit. The Midwestern wonk character is part of his surface appeal. Portman is a softer, less controversial version of the politician who ultimately beat him out to be Romney’s running mate, House Budget Chairman Paul D. Ryan of Wisconsin. Democrats are set to focus all their ammunition on Ryan and the House Republicans who are expected to unveil their budget Tuesday morning.

But Senate Budget Committee members such as Portman will play a crucial role in returning fire on the first Senate Democratic budget in four years, set to be presented Wednesday. Portman is particularly valuable to Budget ranking member Jeff Sessions, who met with the Ohio Republican and a handful of other GOP committee members March 7 to discuss the party’s message heading into budget week.

“He’s a big help,” the Alabama Republican said. “He understands the process, he understands the American economy, he understands the details of the budget requirements. He also has a really good vision for economic growth for America.”

Portman, however, seems uncomfortable talking about his current political efforts. It was no secret that Republican leaders wanted Portman, who helped deliver Ohio for Romney in the GOP primary, to take the reins of the NRSC. The top spot at the campaign arm of the Senate GOP once was a key to moving up the leadership ladder, but with outside spending ballooning and Republican primaries becoming more bruising, the job comes with fewer perks these days. Kansas Sen. Jerry Moran sought the position, and GOP leaders installed two new deputies for him — Portman for finance and Texas Sen. Ted Cruz for grass-roots/tea party outreach.

The move could help boost Portman’s brand if he is successful in matching the more than $40 million the NRSC raised in 2010 from big-ticket donors. But as second fiddle to Moran, he will be insulated from blame if the group repeats its 2012 failure to take back the Senate.

“Portman is very good at positioning himself — when things go well, the buck stops with him, and when things go poorly, the buck stops with someone else,” one top Republican operative said of the NRSC set up.

“He has a level of gravitas and seriousness to him that few have in the conference, and that’s going to make it easier for him to raise money on day one than Sen. Moran,” the operative continued, noting that Moran is not as well-known as Portman, who has national name recognition. “There’s always tension in these things, figuring out with whom does the buck stop. You always wonder in a three-headed beast.”

Portman has already traveled three times to New York City and Florida to meet with donors, an NRSC source said.

But he is careful to defer to Moran, while also loosely outlining his own personal goals.

“He’s the chairman, I’m not,” Portman said. “We work seamlessly together. We meet every week. He’s given me a lot of input into the political side in the sense that I need to be able to explain to donors that we’re doing things differently, and I’ve been able to do that legitimately.”

Portman is reluctant to speak more broadly about what his role will be as the party marches toward 2016. He demurred when asked his thoughts on other ambitious Republicans such as Sens. Marco Rubio of Florida and Rand Paul of Kentucky, both of whom have been aggressively inserting themselves into major issues, including immigration and national security.

Portman, who went through a series of defined roles last Congress, from top Mitch McConnell confidante on budget issues to supercommittee member and top campaign surrogate, only gave a vague vision of his role now.

“I see myself focused like a laser on the big problems like the economy and jobs and the debt and deficit, which are totally related,” Portman said.